Based On The Modified Tung Oil Film Material Coated Urea

The study and development of slow/controlled release fertilizers has become one of the best approaches to increase the efficiency of fertilizers, save the resources and check environment pollution. However, all kinds of slow/controlled release fertilizers in the world all have the disadvantages of using a lot of poisonous solvents, poor biodegradation of the coating, bad abrasion resistance and impact resistance properties and high cost at present. These disadvantages have affected badly the applications of slow/controlled release fertilizers.In this paper, the tung oil from natural product was used for the main original material and was synthesized the modified rung oil (MTO) resin which has large molecular weight and viscosity by chemical method; the curing of the MTO resin was studied by heat or microwave, and the best curing process and conditions were found; the dissolution properties of membranes were analyzed in distilled water and acetone by Soxhlet apparatus; the reactive coating art of MTO resin being on the fertilizer granules was researched in the rotary coating drum and the best coating art was found; a series of the coated fertilizers which have different coating rate and coating structure were prepared, then the coated fertilizers were treated by the method of heat or microwave; the coated ureas' release properties, abrasion resistance and impact resistance properties were evaluated by the methods of soak and leaching, and the factors affecting the coated ureas' release properties, abrasion resistance and impact resistance properties, for example, coating art, coating rate, coating structure and fillers etc, were found; the release rules of several kinds typical of the coated ureas were simulated with mathematical formulas, and base on this, the release mechanisms of the coated ureas were discussed simply; the microstructure of the MTO resin and the exterior shape of the coated ureas were studied by FTIR and SEM respectively.The following conclusions were drawn in this paper. The coating thickness of the coated urea- MTO resin is uniform, 80~150m, and pH of the coated urea is 5.4. Take the sample F5-6-4(t2) for example, the coating rate is 14.3%, urea dissolution percent is less than 9.0% at 24 h in distilled water, 75% release of urea is prolongedfor ~28 days, t80 > 35 days, and the difference of urea dissolution percent is litter before and after the sample F5-6-4(t2) was abraded or impacted. The sample F5-6-4(t2) has met the Trenkel's standards on slow/controlled release fertilizers, and has reached or even exceeded the project target. The dissolution and release rules of the coated urea is expressed by the following relationships: R = At3 + Bt2 + Ct and R = Alnt + B.In this thesis, the main original material rung oil comes form nature, the price of tung oil is cheap, it isn't necessary to use any poisonous solvent during coating process, and the MTO resin membranes have good biodegradation, abrasion resistance and impact resistance properties. That the coated fertilizers prepared with tung oil as the main coating material in the study offered a new technique way for the coated fertilizers industry.